This large-scale retrospective claims database study explored the impact stimulant medication use for ADHD has on future testicular hypofunction risk. The key finding is an increased relative risk for a subsequent diagnosis of hypogonadism among adult male patients who have received long-term pharmaceutical treatment for ADHD with dextroamphetamine, lisdexamfetamine, amphetamine, or dexmethylphenidate. This increased risk was found to be significant when compared to both individuals without ADHD and those with ADHD not using stimulant medications.
Our findings have major similarities and a key difference from the previous large Taiwanese cohort study, which found an association between an ADHD diagnosis and testicular dysfunction (12). Both studies utilized large cohorts to compare rates of testosterone hypofunction in individuals with ADHD retrospectively. While our study did not evaluate the risk of testosterone hypofunction for individuals with ADHD regardless of medication use, we found a significant risk increase among individuals with long-term stimulant use. This conflicts with findings from Wang et al., who found no associated increase in the risk of testicular dysfunction with methylphenidate use among individuals with ADHD but did find a significant increase in testicular dysfunction risk with an ADHD diagnosis. Notably, our study evaluated multiple stimulant ADHD medications in addition to methylphenidate. Wang et al. focused on the effects of hypogonadism on development and puberty, a much younger study population with nearly a 10-year lower mean age (12).
Yet, our findings support conclusions made by the case study from Abdalla et al. that identified a case of reversible pituitary failure leading to hypogonadism believed to be caused by amphetamine-dextroamphetamine (4). Another case report by Ramasamy et al. from 2014 reported on a case of testicular failure and delayed puberty in a 20-year-old male with a 17-year history of methylphenidate use despite cessation of drug use years prior. This patient was treated with supplemental testosterone and human chorionic gonadotropin (5).
One longitudinal study explored this between 2005 and 2011 and found a significantly decreased growth rate among adolescents with a 3-year history of stimulant medication use (13). This treatment length matches the criteria used in our study, but the patient population of focus was on adolescents rather than adults, like the research by Wang et al. (12). With hypothalamic influence over puberty and development involving the release of GnRH and subsequently, LH and FSH (14), a shared physiological pathway may be involved. Methylphenidate has also been found to decrease testosterone levels in male rhesus monkeys, and that dose-dependent decrease in testicular size further supports this idea (8). The same axis is involved in folliculogenesis in females and was found to be impacted in rats with methylphenidate exposure (9). Wang et al. postulated higher dosing relative to mass compared to typical pharmaceutical dosing in many of these animal studies as a reason they did not translate to the results of their research (12). Our study did not have access to medication dosage, so we cannot comment on the potential impact on gonadal functioning.
To our knowledge, this study is the first to identify a significant relative risk of hypogonadism and testicular hypofunction with long-term ADHD medication use. With the number of patients found in TriNet, the power of this analysis is a particular strength, with most current literature supporting our hypothesis consisting of case reports (4, 5, 6). The study size also allowed for propensity matching to minimize treatment selection bias in this population. Limitations of this study design include the lack of information available on the cause of hypogonadism or hormone levels. Also, an inherent bias exists because medication status was not randomized among individuals in the study, and factors such as symptom severity could impact who received pharmaceutical treatment. Despite these drawbacks, the study’s results are significant in helping determine all risks associated with the drug that should be considered by both the patient and healthcare provider when prescribing stimulant medication for ADHD.